// Problem: 
// Contest: 
// URL: 
// Memory Limit: 
// Time Limit: 
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include<bits/stdc++.h>
using namespace std;
#define int unsigned long long
inline int read(){
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
signed main()
{
	int t=1;
//	cin>>t;
	while(t--)
	{
		int a,b,n,t=0,tmp=0;
		cin>>a>>b>>n;
		int x=n/(a*5+b*2)*7;
		n-=n/(a*5+b*2)*(a*5+b*2);
		t+=x;
		int ca=0,cb=0,f=0;
		while(tmp<n)
		{
			if(f==0)
			{
				tmp+=a;
				if(++ca==5)
				{
					ca=0;
					f=1;
				}
			}
			else 
			{
				tmp+=b;
				if(++cb==2)
				{
					cb=0;
					f=0;
				}
			}
			t++;
		}
		cout<<t;
	}
	return 0;
}
